Cardiac valves exhibit two types of pathologies: regurgitation and stenosis. Regurgitation is the more common of the two defects. Either defect can be treated by a surgical repair. Under certain conditions, however, the cardiac valve must be replaced. Standard approaches to valve replacement require cutting open the patient's chest and heart to access the native valve. Such procedures are traumatic to the patient, require a long recovery time, and can result in life threatening complications. Therefore, many patients requiring cardiac valve replacement are deemed to pose too high a risk for open heart surgery due to age, health, or a variety of other factors. These patient risks associated with heart valve replacement are lessened by the emerging techniques for minimally invasive valve repair, but still many of those techniques require arresting the heart and passing the blood through a heart-lung machine.
Efforts have been focused on percutaneous transluminal delivery of replacement cardiac valves to solve the problems presented by traditional open heart surgery and minimally-invasive surgical methods. In such methods, a valve prosthesis is compacted for delivery in a catheter and then advanced, for example, through an opening in the femoral artery and through the descending aorta to the heart, where the prosthesis is then deployed in the aortic valve annulus.
During delivery, the delivery system including the valve prosthesis must be advanced through multiple bends in the patient's vasculature. Some vascular bends will straighten as the relatively stiff delivery system is passed through. However other vascular bends, e.g. the aortic arch, cannot be straightened. Therefore, a typical delivery system bends in a single plane and kinks, or folds onto itself, when advanced through a substantial vascular bend in order to traverse the bend. This bending of the delivery system is presently routine during delivery of the valve prosthesis frame. Bending of the delivery system allows for a longer valve prosthesis frame that can be anchored in the aortic annulus and the ascending aorta.
A typical valve prosthesis frame is made of self-expanding metals, such as Nitinol. The metal structure of the nitinol holds the compressed frame into a tubular structure which resists bending and kinking. Thus, bending, flexing, and/or kinking the valve prosthesis and delivery system during tracking and delivery typically requires a large amount of bending force.
In view of the foregoing, it would be desirable to provide a valve prosthesis that is capable of conforming to a patient's anatomy while providing a uniform degree of rigidity and protection for critical valve components. Protection for critical valve components is essential to maintain reliability for the valve prosthesis. In addition, it would be desirable to provide a delivery system that facilitates bending of the delivery system around a bend and a valve prosthesis that includes a flexible region that is present when the valve prosthesis is compacted for delivery.